In the process of manufacturing a product, a surface of a sheet member, such as a substrate, is often provided with covering material by applying a separate member to the sheet member or by coating the sheet member. The covering material is often inspected manually. Inspection techniques involving no human intervention are disclosed in Patent Document 1 and Patent Document 2, for example.
In Patent Document 1, in order to inspect an object to be inspected of which a surface is covered with a coating that emits fluorescence upon ultraviolet light irradiation, an ultraviolet light image is created based on irradiation using an ultraviolet light source, and a visible light image is created based on irradiation using a visible light source. Based on the visible light image, a position identification unit identifies position information of the object to be inspected. Based on the identified position information of the object to be inspected and the ultraviolet light image, the coating on the object to be inspected is inspected.
In Patent Document 2, in order to inspect whether a printed board is properly coated with desiccant, the desiccant is provided with a fluorescence agent which emits fluorescence. An ultraviolet radiation unit irradiates the printed board with ultraviolet light, and the printed board is photographed by a photographing unit. In a reference information storage unit, reference information concerning regions to be coated with desiccant is stored. Based on an image obtained by the photographing unit, a determination unit determines whether the desiccant is coated in the regions to be coated with desiccant, using the results of comparison of the brightness of an image of a region including a fluorescence region and a predetermined threshold value, and the reference information.